TXA.sub.2 is a metabolite of arachidonic acid widely found in organs of creatures, such as the liver, kidney, lung and the brain, and it is known to have function of strongly coagulating the platelets and contracting the blood vessel ("Cascade of Arachidonic Acid and Drug" by Shozo YAMAMOTO, 1985).
Moreover, it is known that TXA.sub.2 is associated with various diseases such as cardiac infarction, angina pectoris, thrombosis, transient cerebral ischemia, hemicrania, cerebral hemorrhage, cerebral infarction, arteriosclerosis, peripheral circulatory insufficiency or failure, high blood pressure, pulmonary embolism, bronchial asthma, bronchitis, pneumonia, nephritis, hepatitis, and shocks because it strongly contracts the bronchi and the tracheal smooth muscles.
Accordingly, it is expected that effective treatments against the above-mentioned diseases may be obtained by suppressing the action of TXA.sub.2, and many studies have already been reported. For example, Japanese patent publication (Kokoku) 57-35910 discloses 4-(2-phenylsulfonylaminoethyl)phenoxy acetic acid derivatives as compounds which antagonize the action of TXA.sub.2. These compounds, however, are not necessarily satisfactory in terms of the efficacy as pharmaceuticals, lasting ability of the action, adverse side effects and so on.
Under these circumstances, the present inventors have carried out careful studies toward solving the above-mentioned problems, and have found that certain indan derivatives or their salts have a much stronger. TXA.sub.2 antagonizing activity than the above-described 4-(2-phenylsulfonylaminoethyl)phenoxy acetic acid derivatives, leading to the completion of the invention.